A classic illustration of the failure of science in the service of politics was the 1975 study by Robert Heath of Tulane that proved marijuana smoke causes brain damage. When Dr. Heath was finally pinned down, investigators discovered he had fitted rhesus monkeys with gas masks and pumped in marijuana smoke at the rate of 10 joints an hour.^ The brain damage that turned up in the autopsies was caused by oxygen deprivation, not marijuana. Heath could have produced the same results by suffocating his animals with smoke from an oak log.

Unfortunately, the Heath study fits a pattern that characterizes much of official marijuana research. What separates these projects from normal science is that they usually hit the evening news before they’ve been debated in the halls of acadame. Typically, a research group funded by the the U.S Government will find a smoking gun proving that marijuana causes serious physical or mental damage. In time, other researchers discover the claims are flawed and the study is discredited within the scientific community, but the average citizen is stuck with the original headlines. As a result, most Americans believe to one degree or another that marijuana damages the brain, that it lowers testosterone, that it weakens the immune system, that it breaks chromosomes, when in fact there’s no accepted evidence for any of this.

One sure-fire way to hit the front page is to come up with a test result that proves marijuana is a steppingstone to harder drugs—the “gateway theory.” In 1994, the Center on Addiction and Substance Abuse at Columbia University made the shocking announcement that marijuana smokers were 85 times more likely to go on to cocaine than non smokers.^[13] They discovered this by taking the estimated number of cocaine users who had smoked reefer first, and dividing it by the estimated number who hadn’t (almost nobody). Using the same quasi-scientific procedure, you can establish that coffee, alcohol, tobacco, and cherry pie are also precursors. Another headline in this vein hit